This is a simple topic and one which may be of no value if you have a tiny layout.
In my case, with a layout running around the walls, I had 3 mains power outlets all of which would be difficult to access when the layout construction was under way and completed.
This Remote Controller is one of a number that are available which allow you to switch varying number of outlets. This one does the job for me.
Check on-line for pricing (look up: remote control power outlet)
The switched outlet plugs into the wall socket as above. I can turn ON ALL with one switch or select which one I want.
It is also useful for me to divide the layout power into three sections which eases the load when powering up. Others have more than 3 controlled outlets.